S
M
T
W
T
F
S
30
79°
62°
31
77°
68°
1
78°
67°
2
74°
69°
3
80°
67°
4
84°
63°
5
78°
62°
6
76°
64°
7
77°
64°
8
75°
62°
9
76°
63°
10
77°
64°
11
76°
65°
12
78°
65°
13
77°
63°
14
75°
62°
15
71°
60°
16
71°
65°
17
74°
59°
18
69°
56°
19
69°
56°
20
70°
60°
21
74°
63°
22
77°
64°
23
77°
63°
24
76°
61°
25
75°
61°
26
75°
60°
27
76°
61°
28
75°
61°
29
74°
58°
30
67°
54°
1
65°
53°
2
67°
58°
3
72°
59°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Stony Brook
Stony Brook's September 2026 forecast shows daily high temperatures ranging from 65° to 84°, with overnight lows between 53° and 69°. The average high for September is 74° with an average low of 62°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Stony Brook. See also: October | November | December.
